Miocene Grassland Ecosystems Spread Across Continents

Declining atmospheric CO2, increasing seasonal aridity, and intensifying fire regimes drove the expansion of open grassland habitats across North America, East Africa, and Central Asia during the late Oligocene through early Miocene. C3 grasses with silica-rich, fibrous tissues replaced closed forest in continental interiors. Grazing mammals responded with adaptive radiations: horses developed high-crowned teeth for processing abrasive grasses, while new ungulate lineages diversified into the emerging open landscapes.